1. Field of the Invention
The present invention relates to an apparatus for leading to normal tearing of an instrument panel having a built-in passenger air bag (PAB) and, more particularly, to an apparatus for leading to normal cutting of an instrument panel having a built-in PAB, in which, when the PAB is deployed in a low-temperature environment, the instrument panel is generally torn along a tear line without brittle fracture, and particularly a hinge section of the instrument panel is prevented from being exfoliated or splintered.
2. Description of the Related Art
Generally, an air bag is an apparatus that is installed on a driver seat and a passenger seat in order to protect a driver and a passenger. The air bag for the driver seat is designed to be deployed from a steering wheel, whereas the air bag for the passenger is designed to be deployed from an instrument panel, at a predetermined position of which an air bag door is installed and opened toward the passenger.
The air bag for the passenger (or briefly called passenger air bag (PAB)), which is installed in order to protect the occupant of the passenger seat, is mounted on a motor vehicle in the state of an air bag module including an inflator. The air bag door, which is installed in the instrument panel such that the air bag is to be deployed toward the passenger, is called an invisible door that is not be able to be seen in order to improve an exterior view. This invisible door has a tear-off line (hereinafter, referred to as a “tear line”) notched in the instrument panel at a predetermined depth using a laser so as to define a boundary thereof. The air bag door is not separately installed on the instrument panel. In detail, when the tear line is formed in the instrument panel itself using the laser, the instrument panel itself having the tear line serves as the air bag door.
Thus, when the air bag is deployed from the interior of the instrument panel, the air bag door is torn along the tear line by volume expansion of the air bag, and then the air bag comes out of the instrument panel. At this time, in the case of the area such as North America where a low-temperature environment is dominant, a temperature at the instrument panel is very low. As such, when the instrument panel is pressed by the inflating air bag, the tear line is not torn as it stands. In detail, the instrument panel undergoes brittle fracture, so that a tear-off face thereof becomes sharp or that splinters thereof are thrown toward the passenger.
Thus, as illustrated in FIGS. 1 through 3, there has been proposed an apparatus for preventing the brittle fracture of the instrument panel.
FIG. 1 illustrates the configuration of a conventional apparatus for preventing brittle fracture of an instrument panel. FIG. 2 is a cross-sectional view illustrating the structure of an instrument panel in which a PAB is installed. FIG. 3 schematically illustrates arrangement of a tear line and a heater, both of which are formed on a conventional instrument panel.
First, as illustrated in FIGS. 1 and 2, the instrument panel 10 is located under the windshield of a motor vehicle, and particularly in front of a passenger seat. An air bag module 1 causing volume expansion by means of an electrical signal is installed in the instrument panel 10.
As illustrated, a tear line 20 having a “U” shape is formed on the instrument panel 10 such that the air bag module 1 can easily break through the instrument panel 10 in an outward direction during the volume expansion.
Further, a heater 30 is installed inside the instrument panel 10 spaced apart from the tear line 20 by a predetermined interval such that the tear line 20 can be easily torn in a low-temperature environment.
The heater 30 is operated by a controller 50, which receives the signal of temperature at the instrument panel 110 from a temperature detector 40 located in the middle of the tear line 20. When the temperature of the instrument panel 10 is lower than a preset temperature, the controller 50 supplies the heater 30 with electrical power so as to heat a surrounding area of the tear line 20. Thereby, when the tear line 20 is torn off by pressure of the air bag, the instrument panel is neatly and clearly torn along the tear line without brittle fracture.
In this manner, the surrounding area A of the tear line 20 at which the heater 30 is installed is torn when the air bag is deployed, and the other area of the instrument panel 10 at which the tear line 20 is not installed acts as a hinge section B. Part of the instrument panel 10, which is torn along the tear line 20, is folded around the hinge section B in an outward direction, and then the air bag is deployed outwardly.
However, as illustrated in FIG. 3, since the heater 30 is not installed on the hinge section B of the instrument panel 10, and since the heat of the heater 30 is not transmitted to the hinge section B, the hinge section B continues to be under low temperature unlike the surround area A of the tear line 20. Thus, when the air bag is deployed, the hinge section B is folded but the hinge section B is exfoliated, and the resultant splinters are pinched toward the passenger, and cause damage to the passenger.